<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>引入方式</title>
    <style>
        h2{
            color:blue
        }
    </style>
    <!--引入css文件-->
    <link rel="stylesheet" href="my.css">
</head>
<body>
<h1 style="color: red">内联样式</h1>
<h1 style="color: #ff0000">内联样式</h1>
<h2>内部样式</h2>
<h2>内部样式</h2>
<h3>外部样式1</h3>
<h3>外部样式2</h3>

</body>
</html>